By Jonathan Simmons, Guest Columnist

When Jothy Rosenberg was 16 years old his knee locked up while he was jumping rope in gym class. “My dad was a surgeon and told me, ‘Big guys hurt their knees.’ He wrapped me in an ace bandage and said to try and take it easy.”

For a few months Jothy’s knee did seem to get better, until he had another fall. That’s when his parents, both of whom were physicians, thought it might be serious.

Their worst fears were confirmed when a biopsy showed that Jothy had a rare for of bone cancer, Osteogenic sarcoma. “The next day my leg was amputated. At the time [35-years ago] there was no chemotherapy, so that’s the treatment I got.”

Until then Jothy had always been a star athlete. He had set Michigan state records in swimming, and was an expert skier. So it was only natural that after his surgery he asked his doctors and family: “So what can I do?” Meaning, what kinds of sports can I do? Jothy quickly realized: “No one had a clue. We were in uncharted waters and I’d have to figure this out by myself.”

But first he’d have to figure out how to walk.

“I had lost strength and balance and I couldn’t even stand up. It was quite a while before I had the confidence to try sports.” Once Jothy regained his confidence he decided to climb every hill on Mt. Desert Isle. With crutches. “I had blisters and was bleeding from using the crutches. Then I realized I needed to use athletic tape and moleskin. Eventually I did every peak except for Cadillac Mountain.”

Emboldened, Jothy decided to resume swimming “But first I had to figure out how not to go in circles.” From there it was back to the ski slopes, “Which was tough without an outrigger [an assistive device]. But I realized I could do things if I worked hard at it.”

Three-years later, while Jothy was in college, his cancer returned. This time it had spread to his lungs. “I thought I’d been given a death sentence,” Jothy recalled. “But chemotherapy had just been invented at Dana Farber and I survived.”

At that point, Jothy’s motto became, carpe diem: “I dropped out of school and became a ski bum. I also learned how to play 1-legged volleyball and to kayak.” Almost every sport, it seemed, except for biking.

Twelve years ago, Jothy sponsored a participant in the Boston to NY AIDS Ride. “I was bragging to a friend about how far she was biking. He [that friend] told me, ‘I can see you’re excited, it’s a shame you can’t do that bike ride.’”

“That night I bought a bike.”

“At first just doing one mile was tough. Eventually I worked my way up to 25-mile rides. And then I tried hills and learned the hard way that if I didn’t make it up I was in trouble. I couldn’t just stop and then start again, so I had to get stronger to get up every hill. I could not fail.”

For a few years Jothy did the AIDS Ride. “It was a challenge, but I put my mind into Zombie mode and did it.”

And then he heard abut the Pan-Massachusetts Challenge and realized, “That’s about cancer.”

And with that, Jothy was in. Big time. This year will be his 9th ride. He has raised over $100,000 and his team, “Has single handedly raised the money to hire a full time doctor at Dana Farber to research Osteogenic sarcoma.”

Jothy participates in the PMC as a way to give back to the community. But he also rides for personal reasons: “As a kid I had lost my leg and I needed challenges to build my self-esteem. Those challenges and hard work allowed me to have a successful career and to earn a Ph.D.”

That successful career includes earning a Ph.D. in computer science, starting eight high-tech companies, and writing four books. Plus he’s developed a reality TV series about people who’ve “been knocked down by life but courageously fought back, using sports to become even better than they were before.”

So what can Jothy do? Just about anything he wants.